Polycrystalline diamond compacts (PDCs), particularly PDC cutters, are often used in earth-boring drill bits, such as fixed cutter drill bits. PDCs include diamond formed under high-pressure, high-temperature (HTHP) conditions in a press. In many cases, a PDC includes polycrystalline diamond formed and bonded to a substrate in as few as a single HTHP press cycle. A sintering aid, sometimes referred to in the art as a catalysing material or simply a “catalyst,” is often included in the press to facilitate the diamond-diamond bonds that participate both in forming the diamond and, optionally, in bonding the diamond to the substrate.
During use (e.g. while drilling), polycrystalline diamond cutters become very hot, and residual sintering aid in the diamond can cause problems such as premature failure or wear due to factors including a mismatch between the coefficients of thermal expansion (i.e. CTE mismatch) of diamond and the sintering aid. To avoid or minimize this issue, all or a substantial portion of the residual diamond sintering aid is often removed from the polycrystalline diamond prior to use, such as via a chemical leaching process, an electrochemical process, or other methods. Polycrystalline diamond from which at least some residual sintering aid has been removed is often referred to as leached regardless of the method by which the diamond sintering aid was removed. Polycrystalline diamond sufficiently leached to avoid graphitization at temperatures up to 1200° C. at atmospheric pressure is often referred to as thermally stable. PDCs containing leached or thermally stable polycrystalline diamond are often referred to as leached or thermally stable PDCs, reflective of the nature of the polycrystalline diamond they contain.
Although the polycrystalline diamond used in a PDC is typically formed on a substrate, the formation substrate may be subsequently removed, for example to facilitate leaching. Even if the PDC contains polycrystalline diamond on the original substrate, the bond between the polycrystalline diamond and the original substrate may have been weakened, for instance by leaching. Thus, attachment of polycrystalline diamond to a substrate or improving an existing attachment of polycrystalline diamond to a substrate is of interest.